JPH0459692A - Molecular beam source - Google Patents

Abstract

PURPOSE:To effectively prevent the drop in temperature at the opening of a flange by improving a method for supporting a crucible in which a metal to be evaporated is charged. CONSTITUTION:In a molecular beam source in which a heater 4 is disposed on the outer periphery of a crucible 1 for a metal 8 to be evaporated and in which a ring-like flange 1b is disposed at the opening 1a of the crucible 1, the outer peripheral end of the flange 1b is supported with a ring-like supporting member 2 and the supporting member 2 is heated by the thermal radiation of the heater 4.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a molecular beam source in a molecular beam epitaxy apparatus, and in particular to a molecular beam source suitable for preventing a temperature drop at the opening of a crucible containing evaporated metal. Regarding the source.

[Prior art] Molecular beam epitaxy equipment, for example, GaAs
When growing a film, when the temperature of the opening of the crucible of the Ga molecular beam source decreases, Ga adheres to the inner wall of this opening. If Ga is deposited due to the low temperature of the opening of the crucible, surface defects will occur in the GaAs film. By reducing these surface defects, it is possible to improve the yield of semiconductor devices.

Therefore, in order to improve the heating method of conventional molecular beam sources, various improvements have been made regarding the heater structure.

For example, in the technique described in Japanese Utility Model Application Publication No. Sho 61-155376, a heater is disposed only near the opening of the crucible in order to prevent a drop in temperature at the opening of the crucible. Also,
In the technique described in Japanese Unexamined Patent Publication No. 10516/1983, the heaters near the opening of the crucible are doubled.

In any of these conventional techniques, when considering the temperature distribution inside the crucible, the amount of heat released to the outside by thermal radiation near the opening of the crucible is larger than that at the bottom of the crucible. The idea was to deal with this phenomenon by increasing the amount of heat supplied by the heater to the opening of the crucible.

[Problem to be solved by the invention] The above-mentioned conventional technology is appropriate as a heating method, but
If this technology were to be applied to a molecular beam source, it would be necessary to devise ways to support the heater and crucible, but this technology has not been considered.

An object of the present invention is to provide a molecular beam source that can effectively prevent a drop in temperature at the opening of the crucible by improving the technique for supporting a crucible containing evaporated metal. Means] The above object is achieved by supporting the outer peripheral end of a collar provided at the opening of a crucible containing evaporated metal with a ring-shaped support member, and heating the support member by thermal radiation from a heater. achieved.

Further, the above object can also be achieved by supporting the outer circumferential surface of the opening of the crucible on the lower side of the brim with a support member, and by forming the inner circumferential surface of the support member into a comb-teeth shape.

The above object can be achieved even better by arranging a heat shield plate on the upper surface side of the brim and further by attaching a heat shield cap above the opening of the crucible.

[Operation] In general, heating of objects in a vacuum between non-contact objects is done by thermal radiation. The amount of heat at that time is expressed by the following formula.

Q1t=F-work,・A-work・σ (T, 4-T24)
...(1) Here, Q: Amount of heat supplied from object 1 to object 2 F1. : View factor σ indicating how visible object 2 is when viewed from object 1 : Stefan-Boltzmann constant A1 : Area of object 1 T1 : Temperature of object 1 T2=temperature of object 2.

Also, if N shielding objects such as seal plates are inserted between object 1 and object 2, the amount of heat Q'□2 from object l to object 2 is 1. Heat amount Q1
．． is expressed by the following equation.

Q'i! =Q, t/ (N+1)...
(2) Considering the heating of the opening of the crucible of the molecular beam source from the thermodynamic characteristics as described above, the following is found.

In other words, as can be seen from equations (1) and (2), in order to increase the amount of heat supplied from the heater to the opening and brim of the crucible, the shield plate and supporting members of the crucible must be installed to reduce the heat radiation from the heater. It must not be installed between the heater and the opening of the crucible or its support member in such a way as to obstruct it.

Also, considering the heat loss from the opening of the crucible, we can see the following.

That is, the molecular beam source is usually surrounded by a shroud cooled with liquid nitrogen. Therefore, the amount of heat when object 1 in equation (1) is the opening of the crucible and object 2 is the shroud becomes part of the heat loss. In addition, if the opening or brim of the crucible is in contact with other members of the molecular beam source, there is an amount of heat that is removed from that part through thermal conduction.

Therefore, in the first aspect of the present invention, the outer circumferential end of the collar provided at the opening of the five crucibles is supported by a ring-shaped support member. The support member is heated by thermal radiation from a heater. Therefore, it is possible to eliminate the shielding of heat radiation from the heater between the heater and the opening of the crucible. As a result, F in equation (1)
As can be seen from the fact that 1.2 can be made a large value and the value of N in equation (2) can be made zero, it is possible to maximize the amount of heat supplied from the heater to the opening and brim of the crucible. Can be many.

By the way, heat loss due to heat conduction from the outer periphery of the brim provided at the opening of the crucible to the shield plate or the like via the support member depends on the temperature difference between the opening of the crucible and the outer periphery of the brim.

In this respect, in the invention as set forth in claim 1, the support member is also heated by the heat radiation of the heater and becomes high temperature, so that the collar can be maintained at a high temperature, and therefore, heat loss can be suppressed to a minimum.

In combination, the invention according to claim 1 can effectively prevent a drop in temperature at the opening of the crucible.

Further, in the invention according to claim 2 of the present invention, the outer circumferential surface of the opening of the crucible is supported by a support member on the lower side of the crucible brim, and the inner circumferential surface of this support member is shaped like an S tooth. is forming. Therefore, the support member does not substantially serve as a shield for heat radiation from the heater to the crucible opening and flange, so that heat can be effectively supplied from the heater to the crucible opening and flange. Temperature drop can be effectively prevented.

Further, in the third aspect of the present invention, a heat shield plate is disposed on the upper surface side of the flange provided at the opening of the crucible. This makes it possible to reduce the amount of heat taken away by thermal radiation from the brim to the shroud and the like, making it possible to more effectively prevent a drop in temperature at the opening of the crucible.

In the fourth aspect of the present invention, a heat shielding cap is attached above the opening of the crucible. This greatly reduces the amount of heat taken away by thermal radiation from the crucible opening and brim to the shroud, etc.
It becomes possible to more effectively prevent the temperature drop at the opening of the crucible.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

In the molecular beam source of this first embodiment, the opening 1 of the crucible 1
A collar Ib is provided at the upper end of a.

The crucible 1 is supported by crucible guides 3 provided in multiple stages in the axial direction. This crucible guide 3 is also used as a heater guide.

The collar 1b of the crucible 1 is supported by a support member 2 at its outer peripheral end.

A heater 4 is provided on the outer periphery of the crucible 1. This heater 4 is supported by the crucible guide 3.

A heat shield plate 5 is arranged around the heater 4. The heat shield plate 5 is formed by stacking a plurality of thin plates made of a high temperature material such as tantalum.

A presser plate 6 is provided at the upper end of the heat shield plate 5 and extends in the direction of the opening 1b in a hook shape.
The brim 1b and the support member 2 are pressed down.

In addition to the pressing plate 6, a heat shielding cap 7 is attached close to the collar 1b and the upper surface of the support member 2.

The inside of the crucible 1 is filled with evaporated metal 8, which is a vapor deposition material. This evaporated metal 8 is heated by the heater 4 and evaporated.

The heater 4 is connected to a power source (not shown) via a heater lead 10, and this power source is provided with a temperature regulator (not shown).

On the other hand, the crucible 1 is provided with a thermocouple 9 for measuring the heating temperature thereof. This thermocouple 9 is connected to the temperature regulator.

The molecular beam source of this first embodiment is used as follows:
act.

First, the crucible 1 is placed in position so as not to shift due to the fact that it is supported by crucible guides 3 provided in multiple stages in the axial direction and the weight of the evaporated metal 8 housed inside the crucible 1. has been done.

In addition, the opening 1b provided in the opening 1a of the crucible 1 is
The crucible 1 is held in a stable state by being held down by the holding plate 6.

The crucible 1 is heated by thermal radiation from the heater 4, and the evaporated metal 8 inside the crucible 1 is heated by the heat.

The heating temperature of the crucible 1 is measured by a thermocouple 9,
Based on the measurement result, the amount of current supplied to the heater 4 is adjusted by the temperature controller, and when the heating temperature of the crucible 1 is adjusted, the opening 1a and the brim 1b of the crucible 1 are also controlled by the heater 4.
heated by thermal radiation.

By the way, in this first embodiment, as can be seen from FIG. 1, there is no shielding material for the heat radiation from the heater 4 between the heater 4 and the entrance portion 1a and the collar lb of the Ruppo 1. This means that the value of F in the equation (1) can be increased, and N in the equation (2) can be made zero. Therefore, as can be seen from equations (1) and (2) above, the amount of heat supplied by the heater 4 to the opening 1a and the collar 1b of the crucible 1 by thermal radiation can be increased.

As mentioned above, heat loss due to heat conduction from the outer periphery of the collar 1b provided at the opening 1a of the crucible 1 to the shield plate 5, etc. is due to the temperature difference between the opening 1a of the crucible 1 and the outer periphery of the collar 1b. Dependent.

In this regard, the support member 2 is heated by the heat radiation from the heater 4, and the temperature difference between the opening 1a of the crucible 1 and the outer circumference of the brim 1b can be minimized. It is possible to reduce the heat loss taken away by heat conduction to the shield plate 5 etc. through the flange 1b, and the collar 1b is maintained at a high temperature.

Further, in this first embodiment, a heat shielding cap 7 is attached close to the collar 1b and the upper surface of the support member 2. This cap 7 is maintained at a temperature close to that of the heat shield plate 5 due to heat conduction from other members.

As a result of experiments, when T in the above formula (1) is the temperature of the shroud, when the cap is not attached, T, =
77°, whereas when cap 7 was attached, T: 700'K. For this reason, the cap 7 is placed close to the brim 1b and the upper surface of the support member 2.
By installing the
It can be seen that it can be reduced to /4.

In combination with the above effects, according to the first embodiment, it is possible to effectively prevent the temperature of the opening 1a of the crucible 1 from decreasing.

Next, FIG. 2 is a perspective view of essential parts showing a second embodiment of the present invention.

In the molecular beam source of this second embodiment, the aperture 1 of Ruppo 1
The outer periphery of the opening 1a of the crucible 1 is supported by the supporting member 2 at the lower side of the collar 1b provided in the crucible 1.

The inner circumferential surface 2a of the support member 2 is formed into a comb-teeth shape.

Therefore, also in the molecular beam source of this second embodiment,
The opening 1a of the crucible 1 is substantially heated by heat radiation from the heater 4 through the comb-shaped inner peripheral surface 2a of the support member 2.
The top 1b can be directly heated, and a drop in temperature of the opening 1a of the crucible 1 can be prevented.

The other configuration 9 operations of this second embodiment are similar to those of the first embodiment.

Next, FIGS. 3 and 4 show the third aspect of the present invention. FIG. 7 is a vertical cross-sectional view of main parts showing a fourth embodiment.

In the molecular beam source of the third embodiment shown in FIG. ``A U-shaped pressing plate/cap 11 is placed on top.

In addition, in the molecular beam source of the fourth embodiment shown in FIG. 4, a holding plate/cap 12 having a holding part with a U-shaped cross section is provided on the collar 1b and the upper surface of the support member 2 of the lug 1. It is covered.

Pressing plate/cap 11, 1 shown in FIGS. 3 and 4 above
2 also serves as a heat shield plate, and can reliably hold down the crucible through the crucible 1b and reduce heat loss due to heat radiation from the crucible 1b to the shroud or the like.

Next, FIG. 5 is a longitudinal cross-sectional view of a main part showing a fifth embodiment of the present invention.

In the molecular beam source of this fifth embodiment, a plurality of heat shield plates 13 are stacked on the upper surfaces of the supporting members 2 of the upper part 1b and the lower part 1. This heat seal plate 13 is also formed of a thin plate of tantalum or the like, like the heat shield plate 5.

Further, a first
A cap 7 having the same shape as shown in the figure is attached.

As a result, according to the fifth embodiment, it is possible to further reduce heat loss that occurs through heat radiation from the collar b to the shroud and the like.

In addition, the above-mentioned 3. Other configurations 9 of the fourth and fifth embodiments
The operation is similar to that of the first embodiment.

Furthermore, FIG. 6 is a vertical cross-sectional view of the main part showing a sixth embodiment of the present invention.

In this sixth embodiment, a heater 14 is provided inside the cap 7 at a position facing the flange 1b of the crucible 1. This heater I4 is attached to the cap 7 with a bracket 15.

In the molecular beam source of this sixth embodiment, the brim lb of the crucible 1 is forcibly heated by the heater 14 to prevent the temperature of the opening 1a of the crucible 1 from decreasing.

Note that in this sixth embodiment, the support member 2 is not necessarily required and is therefore omitted.

[Effects of the Invention] According to the invention described in claim 1 of the present invention described above, the outer circumferential end of the collar provided at the opening of the crucible containing evaporated metal is supported by a ring-shaped support member, and the supporting member The components are heated by thermal radiation from the heater, and there is no shielding of the thermal radiation from the heater between the opening of the crucible and the brim, so the amount of heat supplied from the heater to the opening of the crucible and the brim is small. Since the support member of the crucible is heated by heat radiation from the heater and the support member 7 material is heated to a high temperature, the heat is transferred from the brim to the lower seal plate. As a result of minimizing loss, it is possible to effectively prevent the temperature drop at the opening of the crucible, which in turn reduces surface defects caused by evaporated metal adhering to the inner wall of the opening of the crucible, and improves the quality of semiconductor devices. This has the effect of improving yield.

According to the second aspect of the present invention, the outer circumferential surface of the opening of the crucible is supported by a support member on the lower side of the baffle, and the inner circumferential surface of the support member is formed into a comb-teeth shape. Also in this invention, the support member does not substantially serve as a shield for heat radiation from the heater to the opening and the collar of the crucible, so heat can be effectively supplied from the heater to the opening and the collar of the crucible. However, it has the effect of effectively preventing a drop in temperature at the opening of the crucible.

Furthermore, according to the invention according to claim 3 of the present invention.

A heat shield plate is arranged on the upper surface side of the brim, and it is possible to reduce the amount of heat taken away from the brim to the shroud etc. by thermal radiation, so the temperature at the opening of the crucible can be reduced.
There is an effect that can be prevented even more effectively.

According to the fourth aspect of the present invention, a cap for heat shielding is attached above the opening of the crucible, and heat is removed from the opening or the brim of the crucible to a shroud or the like by radiation. Since the amount of heat can be significantly reduced, it is possible to more effectively prevent the temperature drop at the opening of the crucible.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a first embodiment of the present invention, FIG. 2 is a perspective view of essential parts showing a second embodiment of the present invention, and FIG.
4, 5, and 6 respectively show the third embodiment of the present invention.
4th. FIG. 7 is a vertical cross-sectional view of main parts showing fifth and sixth embodiments. 1... Crucible, 1a... Opening of crucible, 1b...
A collar provided at the opening of the crucible, 2... A supporting member for the collar or the crucible, 2a... A comb-shaped inner peripheral surface of the supporting member, 3... A crucible guide, 4... A heater, 5 ...
Heat shield plate, 6... holding plate, 7... cap,
8...evaporated metal, 11,. 12... Holder plate and cap, 13... Heat shield plate. 14... Heater. Agent: Tadashi Akimoto, Patent Attorney, Minoru Rake Rere Diagram (S') A Opening Tsubasa 1, 2 Female 74, Pestle 2aw, P1 Guru (inner circumferential surface of 4 Rake Diagram 2, Branch Officer Mark) 4 J- Group

Claims (1)

[Claims] 1. In a molecular beam source in which a heater is disposed on the outer periphery of a crucible containing evaporated metal and a ring-shaped brim is provided at the opening of the crucible, the outer circumferential end of the brim is formed into a ring-shaped A molecular beam source, characterized in that it is supported by a support member, and the support member is heated by thermal radiation from the heater. 2. The molecular beam source according to claim 1, wherein the outer peripheral surface of the opening of the crucible is supported by a support member on the lower side of the brim, and the inner peripheral surface of the support member is formed in a comb-teeth shape. . 3. The molecular beam source according to claim 1 or 2, characterized in that a heat shield plate is disposed on the upper surface side of the brim. 4. Claim 1, 2 or 3, wherein a heat shielding cap is attached above the opening of the crucible.
Molecular radiation source as described. 5. The molecular beam source according to claim 4, further comprising a heater disposed inside the cap at a position facing the brim of the crucible.